1. Field of the Invention
This invention generally relates to telephone networks, and, more particularly, to a system and method for measuring a round trip time delay of voice packets in a telephone network.
2. Description of the Related Art
Typically, telephone systems for private organizations are set up as private branch exchanges (PBX). PBX sites allow for a plurality of telephones to share a set of lines for communicating between the telephones at the site and external telephones. Each telephone is connected to a cabinet. A cabinet is a physical box holding the wires, hardware, and software needed to forward information to and from the telephones.
Most cabinets at PBX sites are connected through physical means, such as fiber optic, connections. This requires many physical connectors be in place. It is preferable to use a local area network (LAN) to connect cabinets at a PBX site because typically all the users associated with that PBX already have a LAN connecting them. One problem with using a LAN is the delays created can distort the voices.
Software measurements of the delay are not accurate because they use an upper layer software protocol, and the coarse granularity software-based timers provides measurements that are sometimes an order of magnitude greater than the actual delays introduced by the network.
It would be desirable to measure delays caused by the LAN so that a customer may be notified of delay problems before the telephone system deteriorates and voices are transmitted distorted. It would also be desirable to know the delay so that if voices are distorted the customer knows that it is the LAN causing the distortion.